The Chicago style presents two types of citation style: humanities style and an author-date system. Chicago style is the basis of Turabian style; i.e. Turabian is a shorter version of Chicago.
Chicago & Turabian style sites
Chicago print style guide available in the GWU Libraries
The Chicago Manual of Style
Multiple copies available in Gelman Reference, Ready Reference, Reserves, Mt. Vernon, and the Virginia Campus: Z 253 .U69
Turabian print style guide available in The GWU Libraries
A Manual for Writers of Research Papers, Theses, and Dissertations : Chicago Style for Students and Researchers
Multiple copies available in Gelman Ready Reference, Mt. Vernon, and the Virginia Campus: LB 2369 .T8 2013